There is a direct communication between the cerebrospinal fluid (CSF) and the perilymph through the cochlear aqueduct (CA). Perilymph depletion due to perilymphatic fistulas has been demonstrated to influence inner ear function, with signs and symptoms similar in many ways to those of Meniere's disease. A leakage of CSF could also theoretically affect the inner ear. The present study was conducted to investigate whether hearing was affected in patients submitted to a leakage of CSF and, if so, to what extent, in which frequency range, which time course and incidence. The study comprised 126 patients who were exposed to different surgical procedures that involved puncture or incision of the dura, and a control group of 32 patients without such leakage. Hearing was reversibly affected only in patients with leak of CSF. The size of the hearing loss, the number of affected patients and the number of frequencies involved increased with increasing amount of CSF lost. Changes in the constituent cochlear fluids due to a transitory reduction in the CSF and the perilymphatic volume with a compensatory endolymphatic expansion may be responsible for the observed findings.